This invention relates to a tennis ball throwing machine, more particularly to one which makes improvement to actuating means for the tennis ball guiding chute.
There is a throwing machine of air compression type applying an air compressor actuated by motor to produce highly compressed air into the throwing tube. When the air pressure is greater than the friction force between tennis ball and the wall of throwing tube, the tennis ball shoots from the throwing tube as does the bullet from the air compressed pistol. However, the throwing machine of air compression type being great in volume, high in manufacturing cost and needing more power is usually suitable for formal tennis training course.
Recently, there was developed a small tennis ball throwing machine provided for family or small tennis court use. Such a small tennis ball throwing machine applies transmission gear actuated by a motor to change speed and make two bats rotate, and a spring to store pressure whereby the bats increase the tennis ball hitting speed. The known tennis ball throwing machines are generally similar in transmission means, however different from one another in means to change the direction of tennis ball throwing on which the effectiveness thereof depends entirely.
One object of this invention is to provide a tennis ball throwing machine which may change in a great variety the tennis ball throwing direction whereby the tennis ball throwing direction is different each time for the user to practice every kind of tennis ball serving direction and reaction.
Another object of this invention is to provide a tennis ball throwing machine which is simple in structure, low in manufacturing cost and convenient in carrying.
A tennis ball throwing machine according to this invention comprises a power supply transmission means which comprises a motor mounted on a frame board, the motor shaft thereof transmitting through a gear wheel the power to a first and second transmission shaft parallel to each other, a bat pivoted on the first transmission shaft, one end of the bat being a hitting portion in a suitable length, the other end thereof being provided with a pivot shaft to pull a tension spring one end of which is secured on the frame board, a cam pivoted on the second transmission shaft, a ball guiding chute made of a long plate with both longitudnal sides bent upward, one end of the ball guiding chute being pivoted on a supporting shaft as a result of which the ball guiding chute may move upward, downward, leftward and rightward, the other end of the ball guiding chute sloping downward to form a bent holding portion at the bottom, and a a tension spring the bottom end of which is in contact with the surface of the cam, characterized in that the axis of the cam which is biased and the second transmission shaft form a sloping angle, and two guiding boards are provided beneath the ball guiding course, the two guiding boards being clamped on both sides of the cam whereby the ball guiding chute driven by the cam may move upward, downward, leftward and rightward to change the throwing direction.
The other characteristics of this invention is that between the holding portion beneath the bottom end of the ball guiding chute and the cam a polygonal eccentric solid is further provided and a shaft of an adjustment button is secured on the eccentric portion at each opposite sides of the polyglnal eccentric solid so that by means of the adjustment button the ball guiding chute may be biased at different heights and when the ball guiding chute is biased at the highest position, the cam in rotation cannot touch the bottom surface of the ball guiding chute where the ball guiding chute maintains at a stable position to keep the throwing direction regular.